计算机网络答案,Computer Networking,A Top-Down Approach,3rd Edition

Computer Networking: A Top-Down Approach

Featuring the Internet

Solutions to Review Questions and Problems

This document contains the solutions to review questions and problems for the 2

Please do NOT copy or distribute this document to others (even other instructors). We’ll

All material © copyright 1996-2002 by J.F. Kurose and K.W. Ross. All rights reserved

2. Suppose Alice, an ambassador of country A wants to invite Bob, an ambassador of

country B, over for dinner. Alice doesn’t simply just call Bob on the phone and say,

“come to our dinner table now”. Instead, she calls Bob and suggests a date and time.

Bob may respond by saying he’s not available that particular date, but he is available

another date. Alice and Bob continue to send “messages” back and forth until they

agree on a date and time. Bob then shows up at the embassy on the agreed date,

4. The Internet provides its applications a connection-oriented service (TCP) and a

connectionless service (UDP). Each Internet application makes use of one these two

services. The two services will be discussed in detail in Chapter 3. Some of the

principle characteristics of the connection-oriented service are:

gaps.

can send into the network, helping to prevent the Internet from entering a state of

grid lock.

The principle characteristics of connectionless service are:

6. The Internet’s connection-oriented service provides reliable data transfer by using

acknowledgements and retransmissions. When one side of the connection doesn’t

receive an acknowledgement (from the other side of the connection) for a packet it

transmitted, it retransmits the packet.

9. At time t

the sending host begins to transmit. At time t

= L/R

completes transmission and the entire packet is received at the router (no propagation

packet to the receiving host at time t

+ L/R

.

services - such as services that guarantee a minimum transmission rate or services

12. One advantage of message segmentation is that it allows for pipelined transmission

Another advantage is that without it, small messages can get stuck behind large

messages in router buffers.

residential or small office; 3. Cable to HFC: residential; 4. 100 Mbps switched

14. A tier-1 ISP connects to all other tier-1 ISPs; a tier-2 ISP connects to only a few of

15. A POP is a group of one or more routers in an ISPs network at which routers in other

ISPs can connect. NAPs are localized networks at which many ISPs (tier-1, tier-2 and

lower-tier ISPs) can interconnect.

16. HFC bandwidth is shared among the users. On the downstream channel, all packets

18. Ethernet most commonly runs over twisted-pair copper wire and “thin” coaxial cable.

19. Dial up modems: up to 56 Kbps, bandwidth is dedicated; ISDN: up to 128 kbps,

multiplexing, and connection setup. Yes, these tasks can be duplicated at different

22. The five layers in the Internet protocol stack are – from top to bottom – the

23. Routers process layers 1 through 3. (This is a little bit of a white lie, as modern